The present invention relates to solar energy collectors. In another aspect, this invention relates to an improved solar collector module with a flat plate absorber which is supported within an evacuated chamber without substantial heat conduction contact between the absorber and the housing. In another aspect, this invention relates to an improved fluid connection configuration for adjacent modules interconnecting the individual modules to form a series-type of solar collector bank.
It has long been recognized that radiant solar energy reaching the earth is an enormous quantity of energy which can be utilized without the undesirable environmental effects present in the production of energy by most conventional sources. To use this energy source, solar collector systems have been proposed which utilize solar radiation to heat a fluid and thereafter either store or use this heated fluid in the production of steam for industrial uses or for powering heating, air-conditioning or the like.
It is necessary that solar collectors be operated efficiently at elevated temperatures so that they can supply fluid at a temperature in the range of 100.degree. C. to 150.degree. C. to be widely applicable for many uses. It is also envisioned that in exceptional cases such as no load conditions the temperature of the absorber itself could reach 320.degree. C. or more.
It has been found that most solar collectors which can operate at these high temperatures do so at a low efficiency and therefore cannot be economically utilized. To increase the efficiency of these solar collectors it is necessary to increase the percentage of the incident energy reaching the absorber and to reduce the energy losses due to such factors as conduction, convection and radiation.
It has been found that flat plate collectors compare favorably with other types of collectors in the percentage of incident radiation reaching the absorber.
To reduce convection losses various complex structures were developed and devised, such as shown in the patent to Godell et al, U.S. Pat. No. 3,227,153 issued Jan. 4, 1966, in which the absorber was enclosed within an evacuated chamber to reduce the convection losses between the absorber and the atmosphere. A similar structure is illustrated in the patent to Coxe, U.S. Pat. No. 1,814,897 issued July 14, 1931.
Although the above described systems have assisted in solving problems present in the design of an efficient solar collector they have not proved entirely satisfactory under all conditions of service for the reason that considerable difficulty has been experienced in providing a structure which could be used with a reasonable size evacuated flat plate collector.
In addition, due to the high operating temperature of the absorbers, heat resistant materials are required in the collector to mount the absorber preventing the use of low-cost, easily manufactured materials.
Therefore, according to one embodiment of the present invention, a solar collector with a flat plate absorber suspended in an evacuated chamber is provided. The absorber and its associated conduits are thermally isolated from the walls of the collector to allow the use of non-heat resistant materials in the construction thereof.